Grain coarsening behaviour of solution annealed Alloy 625 between 600–800°C

As with all alloys, the grain structure of the nickel-base superalloy 625 has a significant impact on its mechanical properties. Predictability of the grain structure evolution in this material is particularly pertinent because it is prone to inter-metallic precipitate formation both during manufacture and long term or high temperature service. To this end, analysis has been performed on the grain structure of Alloy 625 aged isothermally at temperatures between 600 and 800 °C for times up to 3000 h. Fits made according to the classical Arrhenius equation describing normal grain growth yield an average value for the activation energy of a somewhat inhomogeneous grain structure above 700 °C of 108.3±6.6 kJ mol−1 and 46.6±12.2 kJ mol−1 below 650 °C. Linear extrapolation between 650 and 700 °C produces a significantly higher value of 527.7±23.1 kJ mol−1. This result is ultimately a consequence of a high driving force, solute-impeded grain boundary migration process operating within the alloy. Comparison of the high and low temperature values with the activation energy for volume self-diffusion and grain boundary diffusion identifies the latter as the principle governing mechanism for grain growth in both instances. A decrease in the value of the time exponent (n) at higher temperatures despite a reduction in solute drag is attributable to the Zener pinning imposed by grain boundary M6C and M23C6 particles identified from Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDXS) analysis. Vickers hardness results show the dominance of intermetallic intragranular precipitates in the governance of the mechanical properties of the material with grain coarsening being accompanied by a significant increase in hardness. Furthermore, the lack of any correlation with grain growth behaviour indicates these phases have no significant effect on the grain evolution of the material

Carotid Intima-Media Thickness Progression as Surrogate Marker for Cardiovascular Risk Meta-Analysis of 119 Clinical Trials Involving 100 667 Patients

Background: To quantify the association between effects of interventions on carotid intima-media thickness (cIMT) progression and their effects on cardiovascular disease (CVD) risk. Methods: We systematically collated data from randomized, controlled trials. cIMT was assessed as the mean value at the common-carotid-artery; if unavailable, the maximum value at the common-carotid-artery or other cIMT measures were used. The primary outcome was a combined CVD end point defined as myocardial infarction, stroke, revascularization procedures, or fatal CVD. We estimated intervention effects on cIMT progression and incident CVD for each trial, before relating the 2 using a Bayesian meta-regression approach. Results: We analyzed data of 119 randomized, controlled trials involving 100 667 patients (mean age 62 years, 42% female). Over an average follow-up of 3.7 years, 12 038 patients developed the combined CVD end point. Across all interventions, each 10 μm/y reduction of cIMT progression resulted in a relative risk for CVD of 0.91 (95% Credible Interval, 0.87–0.94), with an additional relative risk for CVD of 0.92 (0.87–0.97) being achieved independent of cIMT progression. Taken together, we estimated that interventions reducing cIMT progression by 10, 20, 30, or 40 μm/y would yield relative risks of 0.84 (0.75–0.93), 0.76 (0.67–0.85), 0.69 (0.59–0.79), or 0.63 (0.52–0.74), respectively. Results were similar when grouping trials by type of intervention, time of conduct, time to ultrasound follow-up, availability of individual-participant data, primary versus secondary prevention trials, type of cIMT measurement, and proportion of female patients. Conclusions: The extent of intervention effects on cIMT progression predicted the degree of CVD risk reduction. This provides a missing link supporting the usefulness of cIMT progression as a surrogate marker for CVD risk in clinical trials

Generalized geologic map of the crystalline rocks in central Maryland, southern Pennsylvania, and Delaware

This digital image was produced in the Summer of 2012 by the Maryland State Archives (MSA) from the original map held by the Maryland Geological Survey (MGS). We are indebted to the staff of the MGS and MSA for helping us make this these images available.This map is Plate 3 from Fisher, G.W., “Geological Interpretations of Aeromagnetic Maps of the Crystalline Rocks in the Appalachians, Northern Virginia to New Jersey”. Baltimore: Maryland Geological Survey, 1979 (Report of Investigations No. 32)

Aeromagnetic map of central Maryland, southern Pennsylvania, and Delaware showing generalized geologic relations of the crystalline rocks

This digital image was produced in the Summer of 2012 by the Maryland State Archives (MSA) from the original map held by the Maryland Geological Survey (MGS). We are indebted to the staff of the MGS and MSA for helping us make this these images available.This map is Plate 2 from Fisher, G.W., “Geological Interpretations of Aeromagnetic Maps of the Crystalline Rocks in the Appalachians, Northern Virginia to New Jersey”. Baltimore: Maryland Geological Survey, 1979 (Report of Investigations No. 32)

Aeromagnetic map of eastern Pennsylvania and northern New Jersey showing generalized geologic relations of the crystalline rocks

This digital image was produced in the Summer of 2012 by the Maryland State Archives (MSA) from the original map held by the Maryland Geological Survey (MGS). We are indebted to the staff of the MGS and MSA for helping us make this these images available.This map is Plate 1 from Fisher, G.W., “Geological Interpretations of Aeromagnetic Maps of the Crystalline Rocks in the Appalachians, Northern Virginia to New Jersey”. Baltimore: Maryland Geological Survey, 1979 (Report of Investigations No. 32)